1. Field of the Invention
This invention relates to a method for forming an aluminum or aluminum alloy film in a fine pattern without using a photo resist.
2. Description of the Prior Art
In prior art techniques, an aluminum film has been commonly used for electrodes or leads of semiconductor devices such as Large Scale Integrated circuits (hereinafter called LSI).
FIG. 1 is a partial cross sectional view of an LSI which shows a prior method for forming aluminum film in a desired pattern. A silicon-dioxide film 2 is formed on a semiconductor substrate 1. An aluminum film 3 is disposed on the silicon-dioxide film by a vaporizing process.
In the first step, as shown in FIG. 1a, a photo resist film 4 is formed on the aluminum film 3 in the desired pattern by a photo deposition technique.
In the second step the aluminum film 3 is selectively removed in order to form the desired pattern, as shown in FIG. 1b. In this step, the photo resist film 4 protects the aluminum film 3 against etching.
This prior method requires many steps such as forming a photo resist film, selectively exposing the resist film to light, developing the lighted region, baking and removing the resist film.
Because the accuracy of a fine aluminum pattern depends upon the accuracy of the steps described above and on the contrast achieved during the development of the photo resist 4, this prior art method is limited in its accuracy. Moreover, a reduction in productivity is caused by the imperfect removal of the photo resist.